This invention relates to a method for producing a planar type electron radiating field emission structure used for a flat panel display and, more particularly, to a flat type electron radiating device for radiating electrons from a plurality of pointed end cathodes.
Investigations are presently being conducted into planar type image display devices as image display replacements for the currently employed CRT for television receivers. Such planar type image display devices are exemplified by liquid crystal displays, electroluminescence devices and plasma display panels. A field emission type image display device is also attracting attention in respect of display luminosity on the viewing screen surface.
In a field emission type image display device a number of conically-shaped cathodes, such as of molybdenum, with a diameter of not more than 1.0 .mu.m, formed on a substrate by a semiconductor producing process, are used as radiation sources, and a plate-shaped gate electrode, provided with holes in register with the cathodes, is formed at the distal ends of the cathodes. The gate electrode is spaced apart from the distal ends of the cathodes and a high electrical voltage is applied across the gate electrode and the cathodes to produce field emission and extract an electron beam from the cathodes. This electron beam is irradiated on light emitting particles (phosphors) arranged on the back side of an anode to display a desired picture such as on a camcorder viewfinder screen, instrument display panels, computer monitors and television displays.
A wide variety of processes have been proposed and/or are used to produce electron-radiating devices or field emission structures and reference is made to U.S. Pat. Nos. 243,252; 5,278,472; 5,219,310; 5,188,977 and 5,007,873 for their disclosures of such processes.
The known processes involve one or more steps requiring expensive tooling, such as dry etching and evaporation, gate patterning with photo tools having extreme accuracy, use of a glancing angle evaporator to avoid shorting of cone vias, and other related steps which increase processing time and expense and require extreme precision.
For example, the patterning of the gate metal in certain prior known processes requires the use of a photo tool with greater than 1 .mu.m resolution because the final width or diameter of the gate is controlled solely by the photo tool. This also necessitates the use of a relatively thick gate electrode layer, and the use of rotational glancing angle evaporation of the underlying insulating layer to form cathode vias which are wider than the gate opening, in order to avoid shorting of the cathodes.
Therefore the present process for producing planar field emission structures evolved from the need to overcome the aforementioned disadvantages and to provide a new process which is simplified, rapid, flexible, inexpensive and commercially practical for the production of planar field emission structures or devices.